Beneficiation of fluorspar ores



United States Patent [72] Inventors George E. Allen Boulder, Colorado; Glenn E. Allen, Rio Verde San Luis Potosi, Mexico [21] Appl. No. 848,079 [22] Filed Aug. 6, 1969 [45] Patented Oct. 27, 1970 [73] Assignee Allied Chemical Corporation New York, New York a corporation of New York Continuation-impart o1 Ser. No.

744,140, July 11, 1968, abandoned, which is a continuation of Ser. No. 478,858, Aug. 11, 1965, now Pat. No. 3,430,765

[54] BENEFICIATION OF FLUORSPAR ORES 13 Claims, No Drawings [52] 11.5. C1 209/11, 209/ 167 [51] Int. Cl B63b 1/02, 803d 1/06 [50] Field of Search 209/1 1, 166. 167

[56] References Cited UNITED STATES PATENTS 1,914,695 6/1933 Lange 209/166 2,105,826 1/1938 Tartaron 209/166 3,138,550 6/1964 Woolery 209/166X 3,382,976 5/1968 Mercade 3,430,765 3/1969 Allen ABSTRACT: Acid-grade" fluorspar is recovered from fluorspar ores containing appreciable amounts of gangue minerals by a froth flotation treatment in a one-step fluorspar flotation circuit which comprises the steps of mixing crude fluorspar ore with water to form an aqueous pulp, adding to said aqueous pulp a water-soluble ferrous salt in an amount to provide between 0.2 and 0.8 pounds of ferrous salt per ton of crude fluorspar ore, adding to the pulp a collector for fluorspar, said collector selected from the group consisting of saturated fatty acids, mixtures of saturated and unsaturated fatty acids wherein the saturated fatty acid content of the mixture comprises at least about 30 percent of the total quantity of collector present and soaps of these acids or acid mixtures, and at least one depressant for gangue minerals selected from the group consisting of alkali metal silicates, alkali metal metasilicates, and quebracho, conditioning this mixture by heating said pulp to its boiling point with agitation While maintaining said pulp at a pH between about 8.0 and 9.0, subjecting said conditioned pulp to froth flotation thereby producing a froth rich in fluorspar and recovering in excess of 80 percent, based on the fluorspar from said froth. A further finding is that use of guar in this system increases the recovery of acid grade fluorspar.

BENEFICIATION OF FLUORSPAR ORES CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. application Ser. No. 744,l40, filed July I1, 1968 now abandoned by George E. Allen and Glenn E. Allen for Beneficiation of Fluorspar Ores, which application in turn is a continuation-inpart of U.S. application Ser. No. 478,858, filed Aug. 1 1, I965, now US Pat. No. 3,430,765.

"Acid-grade fluorspar, a term generally utilized to designate a concentrate containing at least 97 percent fluorspar (C215), is used in various chemical processes as a source of fluorine and hydrogen fluoride. The specifications as to allowable inpurities vary with the industry but, in general, it is required that the fluorspar product be relatively free of gangue minerals such as quartz, calcite, clays and barite, as well as other accessory minerals including various sulfides such as galena, sphalerite, pyrite. and chalcopyrite. Fluorspar ores as mined seldom meet the specifications either with respect to fluorspar content or freedom from impurities and suitable methods of concentration and ore separation must be employed to recover commercial acid-grade products from fluorspar ore. Although the beneficiation of fluorspar ores is readily effected by use of so-called anionic flotation reagents such as fatty acids, tall oils and the like, as well as various soaps thereof, the elimination of certain mineral impurities from the concentrate, thereby improving fluorspar grade, has been a difficult and costly task.

In the past a great many techniques have been employed to recover acid-grade fluorspar and generally these invlolve the addition of a plurality of special additives, e.g. sulfliydryl or xanthate collectors, which together with metallic salts subsequently interfere with the subsequent flotation of fluorspar. Additionally, it has been a common practice to have more than one flotation circuit to effectively remove the impurities from the fluorspar, thereby necessitating additional equipment which contributes to the milling costs in recovering an acid-grade fluorspar.

It has now been found that fluorspar ores containing in addition to fluorspar values appreciable quantities of gangue minerals may be concentrated to produce a fluorspar enriched concentrate having a fluorspar concentration of at least 97 percent in a one-step fluorspar flotation circuit by providing in the aqueous pulp of crude fluorspar ore minor amounts of a water-soluble ferrous salt, provided said ore does not contain the ferrous salt in the desired amounts. In issued Pat., US. Pat. No. 3,430,765, there was no recognition that if the fluorspar ore did not contain a water-soluble ferrous salt in an amount between 0.2 and 0.8 pounds per ton of crude fluorspar ore that the process disclosed in the patent provided only one advantage using the particular collector acids used, a lower silica content. However, it was found that when a water-soluble ferrous salt was added to the aqueous pulp both silica and carbonate could be held to acceptable limits while obtaining increased recovery of acid-grade fluorspar. This provides a definite depressing of sulfides, carbonates, silica and clay not obtainable if the water-soluble ferrous salt were not originally present or not added to the fluorspar ore prior to the conditioning step.

A further finding is that when guar is added to the aqueous pulp and conditioned in the presence of the particular collector acids employed in this process the clay slimes, barium sulfate and other gangue minerals are effectively blocked out, thus resulting in increased recovery of acid-grade fluorspar. The guar may be added with the normal depressants employed, e.g. alkali and alkaline silicates and metasilicates and quebracho.

When an aqueous fluorspar pulp is conditioned in the presence of the water-soluble ferrous salt, preferably in combination with guar, under the conditions of the present process, a froth rich in acid-grade fluorspar is selectively formed in a one-step fluorspar flotation circuit while gangue pyrite, are effectively separated from the fluorspar.

In accordance with the present invention, a fluorspar enriched concentrate having a fluorspar content of at least 97 percent is obtained from crude fluorspar ores containing in addition to fluorspar appreciable amounts of gangue minerals by mixing the crude ore with water to form an aqueous pulp, adding to the pulp a water-soluble ferrous salt in an amount to provide in the aqueous pulp about 0.2 to 0.8 pounds of ferrous salt per ton of crude ore, concentrating the pulp, adding to said pulp a collector for fluorspar selected from the group consisting of saturated fatty acids, mixtures of saturated and unsaturated fatty acids wherein the saturated fatty acid con-'* tent of the mixture comprises at least about 30 percent of the total quantity of collector present and soaps thereof and adding at least one depressant for gangue minerals selected from the group consisting of alkali metal silicates, alkali metal metasilicates and quebracho, heating the pulp with agitation at its boiling temperature while maintaining said pulp at a pH between about 8.0 and 9.0, subjecting said pulp to froth flotation thereby forming a froth rich in fluorspar and recovering said fluospar concentrate from the froth. Preferably, the guar is added to the pulp at this point.

In this process the fluorspar collector must be comprises, at least in part, of a saturated fatty acid or soap thereof is the one-step fluorspar flotation circuit for the selective flotation of acid-grade" fluorspar is to be successful. Contrary to prior art procedures in which fatty acid collectors having a relatively high unsaturated fatty acid content, such as oleic acid and tall oil acids are conventionally employed, we have found that conditioning of the aqueous pulp in the presence of fully saturated fatty acid collectors or soaps thereof, present in an amount of at least 1.5 pounds per ton of ore milled, is essential in obtaining a fluorspar product of desired acid-grade" purity. If desired, a portion of the saturated fatty acid collector may be replaced with an unsaturated fatty acid or soap thereof, provided that the saturated fatty acid content of the collector comprises at least about 30 percent, preferably between about 30 and 60 percent, of the total quantity of collector present. Moreover, by employing a saturated fatty acid collector, high recoveries, generally in excess of percent of the fluorspar content present in the crude ore are effected. If the aqueous pulp is conditioned in the presence of unsaturated fatty acid collectors alone, such as oleic acid, or in the presence of a commercial preparation containing predominantly unsaturated fatty acids, substantially lower recoveries of the fluorspar content of the crude ore are obtained and the fluorspar concentrate resulting from such a one-step flotation procedure is contaminated with excessive amounts of minerals, precluding obtainment of an acid-grade" product.

The fatty acids and soaps thereof employable as collectors in the present process are well-known materials. Included within the term soaps are the alkali metal and alkaline earth metal soaps such as sodium; potassium, calcium, magnesium and aluminum soaps. Suitable saturated fatty acids include acids containing from about 4 to 22 carbon atoms, preferably 12 to 18 carbon atoms, in the molecule'such as palmitic acid, Iauric acid, stearic acid, commercially available preparations containing minor amounts of unsaturated fatty acids such as Hyfac 423,I-Iyfac 425, Hyfac 400 made by Emery Industries, Inc.; and Swift 55, Swift 62, Swift RG made by Swift and Company, etc., all of which contain at least about 80 percent saturated fatty acids. Accordingly, as used in the present case, the term saturated fatty acid is intended to include such mixtures of fatty acids as are found in coinmercial products. If desired, unsaturated fatty acids containing from about l2 to 20 carbon atoms in the molecule such as crude and purified oleic acid, palmitoleic acid, linoleic acid, distilled tall oils, commercial preparations containing a major amount of unsaturated fatty acids such as Acintol FAI tall oil fatty acid and Acintol FA2 tall oil fatty acid produced by the Arizona Chemical Company; Emersol 2l 1 low-titer oleic acid, Emersol 531 distilled tallow fatty acid and Erntall 665 fractionated tall fatty acid made by Emery Industries, Inc., etc., may be used in conjunction with the saturated fatty acids. Although the amount of fatty acid collector used may be varied widely,

amounts of about 1.5 to pounds p er ton of ore milled are generally satisfactory. lt'is necessary, however, when commercialsaturated fatty. acid preparations and mixturesof saturated and unsaturated fatty acids are employed that the saturated fatty acidcontent of the collector comprise at least about 30 percent, preferably between about.30 and 60 percent, of the total quantity of collector present-to effect selec- 1 an alkaline reagent such asan alkali metal hydroxide or carbonate, e.g. sodium hydroxide or sodium carbonate. in some instances, the addition of sufficient quantities of fatty acid col- V lector and gangue mineral depressant will givea'pulp of suitable pH without the addition of any other, pH modifying agent. i V

The composition of the ores treatable: inyabcordancewith the present invention generally comprises from about'40 to 90 tive flotation of the'tluorspar values contained in the ore. The

preferred collector is cornprised of mixtures of saturated and unsaturated fattyacids having from. 12 to '18 carbon atoms and having a saturated fatty. acid content between about 30 and 60 percent. 7

ln effectingthe one step fluorspar flotation circuit for the recovery of the acid grade fluorspar values contained in the L crude ore in accordance with the present process, it has been found necessary to add at leastone of an alkali metal silicate,

metallic salt contaminants and minor quantities of oth'enimpualkali metal metasilicate, such as sodium silicate or sodium metasilicate, or quebracho in conjunction withpthe fatty acid 7 collector during the conditioning step of the process. In addi:

tion to these reagents guar has been found unexpectedly efi'ective in combination with theuse of the ferrous saltadded. While certain of these reagents may act together with the pH regulator as an alkalinity. modifier, under the conditions of the present process such reagents also serve as depressants for The quantity of additive employed may also be varied widely and, in general, satisfactoryresults are obtained when .-.the depressant is used in an amount offrom about 0.1 to about 6,

1 preferably from about 0.2 to about 5 pounds per ton of ore milled. The amount of silicate generally employed'may range gangue minerals and disperse slimes, thereby permittingselec- 1 tive flotation of thefluorspar values by the fatty acid collector.

percent calcium fluoride, up to about 50 or more percent gangue minerals such-as quartz and calcite, up to about lSpercent sulfide minerals including gale na, sphalerite andpyrite, minor amounts normally less than about 3 percent of complex rities.

methods, the dry ore is crushed and ground sufficiently to pass a 48 mesh screenaThe fineness of the grindmay vary from 60 v to 90 percent,200 mesh depending on' the locking. characteristics of the ore. However, substantially complete liberation of the fluorspar from ,the gangue is required for a satisfactory separation and .theflneness of grind should be selected ac-. 1 cordingly. The ground ore is then mixed with sufficient quantities of water in a ball mill. to form an aqueous pulp having a solids content of about 60 to 80 percent by weight based on the weight of the pulp. Although localwater suppliesmay ordinarily be employed in forming the pulp, softened water hav- 3 ing a total hardness of not greater than about 200 p.p.m..is preferred since the use of softened water reduces the fatty from about-2 to 6 pounds per ton of ore milled. The amount of quebracho used is, generally between about 0.2 and 0.8

pounds per ton of crude ore, but can vary widely.

As mentioned above, itchas been found that guar when added in combination with the water-soluble ferrous salt effectively blocks out clay slirnes, barium sulfate and other gangue minerals and resultin increased fluorspar recovery. The guar suppresses the slimes and gangue so that it does not float acid requirements in collection of thefluorspar rich froth; If the crude oredoes not'contain a water-soluble ferrous salt such as ferrous sulfate it is addediri amounts to provide about 0.2 to 0.8 pounds per ton of crude ore.

Thereafter, the solid particles contained in the aqueous pulp or slurry areclassified to producea pulphaving a particle size suitable for flotation, generally ranging from about 48 mesh to a 10 microns. The aqueous pulp is then fed to a concentrator or when the collector acid(s) is added. Theguar can be addedto the grindingmill or conditioner ator near the same point of thickener to form a pulp having a solids content of about 35 to percent by weight based on the weight of thepulp, and the water obtained as a result'o f thickening'of the pulp is withdrawn as waste from the concentrator by any conven tional manner as by decantation, Preferably, it is at this point addition as the water-soluble ferrous salt and the depressants empl'oyed..Preferably, the guaris added to the aqueous pulp prior to the conditioning step so that the "guar and aqueous pulp are for about 2 tolO minutes prior to the addition ofthe collector acid(s). Howevenin some applications the addition of the guar simultaneously'with the conditioning agents has been found effective. Guar is compatible with the otherage'nts added as a dry powder or as an aqueous dispersion in amounts used in theflotation process of this invention andmay befl o of about 0.1 to 0.7, preferably 0.2 to 0.5, pounds per ton of ore milled with smaller amounts adequate for. the higher grade i fluorspar ores and increased amounts for the lower grade ore.

During the conditioning'ofthe aqueous pulp it hasbeen found that in order to obtain a .fluorspar concentrateof the it desired purity the conditioning should be effected at its boiling temperature at apH in the range of about 7.0 to 10.0, preferably 8.4 to 8.8, for a minimum period of time, generally at least about 5 minutes. "After boiling the pH willbe lowered and will vary from about 7 to 9.0, with a pH of 8.4 to 8.8 considered optimum. Unless conditioning is effected atthe pH- of .the minerals present in the pulp will be floatedtogether with the desired fluorspar. Sirice.different fluorsparores. will ranges, temperature and time specified, substantial quantities give varying pH valuesrwhen slurried. in .water, it'is usually .7 necessary to adjustthe pH of the pulp with a conventional pa i i regulating reagents. ThepH regulator may beadded' to-the pulp at any time before completion'of the conditioning stage,v of the process but it is preferredto add the requisite quantities lator to adjust thepHofpulpto a valu e between 7.0 and 10.0, preferably between 8 and 9.='lf desired, a portion of the r of pH. regulator necessary to maintain the pH within the stated N values simultaneouslywith the fatty acid collector and gangue mineral depressant prior to conditioning of the pulp.A pulpof i too low pH may be brought to the desirable pH by addition of.

in the process at which the guaris added. If desired, any commercial flocculating or agglomerating agent may be employed in the concentrator to assist in settling of the pulp. In acditions employed, the complex matallic salt contaminants-are precipitated, carried over into the fluorspar froth flotation circuit and therein interfere with the. selective flotation of the desired fluorspar values. In the process of this invention the amount of contaminants carried over is suft'rciently small so as not to interfere with the selective flotation.

After the aqueous pulphas been classified and concentrated to produce a pulp having a" particlesize and solids content suitable for flotation, the pulp is fed. into a conditioning tank where itis heated to its boiling point with agitation. The boiling temperature of the pulp may be higher or lowerthan 2;12F-. depending uponthe atmospheric pressure at the point of location of the operation. Although the practice of the present invention is not limited to any particular order of addi- V tion of the separate conditioning reagents, it is preferred, however, to properly condition the pulp after the requisite quanti-.:

ties of fatty acid collector and gangue depressant have. been added tothe pulp together with-suitable quantities of pH regurequisit'e. quantity of the fatty acid collector and I gangue depressant may be addedtot hepulpprior to heating and the remaining quantities may then beadded to the pulp either in-v ln practicing theinvention, the fore is first prepared for. flotation by conventional methods l n accordance. with thesetermittently or continuously during conditioning at the boiling temperature of the pulp.

Although any conventional apparatus having external or internal heating means may be employed to condition the pulp, a preferred procedure involves introducing sufficient quantities of steam into the conditioning tank as through pipes discharging below the pulp level to bring the pulp to its boiling temperature. Sufficient conditioning of the pulp is normally achieved as the pulp is brought to its boiling temperature with agitation. However, it is generally necessary to condition the pulp at its boiling temperature for a period of 5 to 60 minutes, preferably to 45 minutes, especially if high recoveries of the fluorspar content contained in the pulped ore are to be realized. After conditioning of the pulp has been completed, the pulp, at or near its boiling temperature, or after being allowed to cool to ambient temperatures, is then froth floated by customary mechanical or pneumatic methods to produce an enriched fluorspar froth and a tailings product essentially free of fluorspar and containing the gangue materials and sulfide minerals. In general, the solids content of the pulp after conditioning is reduced to about to percent be weight based on the weight of the pulp.

The froth product may contain some quartz, calcite, or other gangue materials collected with the fluorspar in the initial frothing operation. The froth is generally refloated to recover the fluorspar and reject the remaining gangue materials. One or more such cleaning operations generally suffices to yield final fluorspar enriched concentrates having a fluorspar content of at least 97 percent and essentially free from gangue and other impurities. Additional reagents, such as a small quantity of alkali metal silicate or quebracho may be used in the cleaning operations to facilitate rejection of the gangue impurities. The tailings material, resulting from the cleaning operations, may be recycled to preceding flotation steps or other convenient points in the flotation or grinding circuit for retreatment, or may be, rejected as waste.

As mentioned above, the water-soluble ferrous salt should be present in, or added to the aqueous pulp preferably before concentrating the pulp, in an amount to provide about 0.2 to about 0.8 pounds of ferrous salt per ton of crude ore milled. One way which has successfully been used achieving this in the pulp is to add to the pulp a sufficient amount of a 10 percent by weight aqueous solution of the ferrous salt, such as ferrous sulfate, to provide an amount of ferrous salt within the above limits. The upper limit of the specified range is dictated by economics and thus natural ores having higher water-soluble ferrous salt contents can be used without difficulty.

The water-soluble ferrous salts are believed to function by the association of the ferrous ion with the gangue materials, giving the gangue materials a greater affinity for water. The combination of the use of a water-soluble ferrous salt with a collector comprising at least 30 percent saturated fatty acids as specified above has been found to yield unexpectedly superior acid grade fluorspar recovery. Although the water-soluble ferrous salt is preferably added to the pulp at the ball mill, it can also be added with the collector if desired.

It will be apparent to anyone skilled in the art that the process of this invention can be operated as a batch, intermittent batch or as a continuous process by means of recognizable variations in the apparatus and use thereof.

The following examples, while not intended to limit the scope of the invention, are illustrative of the benefits derived from the practice thereof. The ores of Examples 1 and 2 were found to contain sufficient ferrous salt so as not to require the addition of the salt. These Examples exemplify the process of US. Pat. No. 3,430,765.

EXAMPLE I A crude broken fluorspar ore consisting essentially of fluorspar associated with appreciable quantities of a siliceous gangue composed predominantly of quartz, metallic sulfides including galena, sphalerite and pyrite, and minor amounts of sulfur (present as complex metallic salt contaminants) was obtained from a Colorado deposit. The ore had been stored underground in the mine for a period of about 52 weeks after being mined. The crude ore assayed 46.9 percent CaF 32.2 percent SiO,, 6.0 percent metallic sulfides, 2.5 percent CaCO and 2.0 percent S. overflow The crude ore was subjected to staged crushing, screening, wet grinding and classifying operations to produce an aqueous pulp containing solids having a particle size such that 67 percent passed through a 200 mesh screen. The pulp discharging from the ball mill wherein the ore was wet ground had a solids content of 68 percent, based on the weight of the pulp, and the classifier overflow was maintained to produce a pulp having a solids content of 16 percent, based on the weight of the pulp. The water used for wet grinding of the ore contained the equivalent of 100 ppm. total hardness. Separan, a commercial flocculating agent, was added to the classifier overflow product in an amount equivalent to 0.04 pound per ton of ore milled to assist in settling the pulp.

The aqueous pulp was then thickened by decantation to produce a pulp having a solids content of about 40 percent, based on the weight of the pulp. The thickened pulp was then transferred to a conditioning tank to which there was added the equivalent of 1.9 pounds per ton of l-lyfac 400, a commercial hydrogenated fatty acid comprised of about percent saturated fatty acids containing from 14 to 18 carbon atoms, the equivalent of 2.3 pounds per ton of Acintol FA2, a tall oil fatty acid comprises of about 50 percent oleic acid and 46 percent linoleic acid, the equivalent of 4.7 pounds per ton of sodium silicate and sufficient sodium carbonate (equivalent of 14.0 pounds per ton) to bring the pulp to a pH of about 8.8. The pulp was then conditioned at its boiling temperature (201F.) by introducing steam at a temperature of 352F. and 75 p.s.i. through pipes discharging below the pulp level for a period of 20 minutes.

After conditioning, sufficient water was added to the pulp to produce a pulp having a solids content of about 25 percent by weight based on the weight of the pulp. The diluted pulp was then continuously fed into the first cell of a bank of flotation cells to which air was continuously introduced, thereby resulting in formation of a compact, heavily mineralized fluorspar froth. The underflow comprising the tailings was 'rich in gauge and sulfide materials. The rougher froth was then cleaned by refloating in a series of flotation cells. The final fluorspar eoncentrate assayed 97.07 percent Cal 0.94 percent SiO 0.85

percent CaCO 0.002 percent metallic sulfides and no complex metallic salt contaminants and accounted for a recovery of 90.8 percent of the fluorspar in the ore.

EXAMPLE 2 A crude fluorspar ore assaying 51.1 percent CaF 31.0 percent SiO 3.0 percent CaCO 6.0 percent sulfide minerals and 2.0 percent S (present as complex metallic salt contaminants) was processed for recovery of fluorspar values contained therein in accordance with the procedure described in Example 1 except that essentially saturated fatty acids, l-lyfac 400, present in an amount equivalent to 4.0 pounds per ton of ore milled, was used as the sole collector.

in this example, sodium silicate was added to the concentrated pulp together with the hydrogenated fatty acid collector in an amount equivalent to 3.2 pounds per ton of ore milled, and sufiicient sodium carbonate (equivalent to 18.7 pounds per ton) was added to bring the pH of the pulp to a value of 8.4. The pulp was conditioned, floated and cleaned in the same manner as in the preceeding example. The final fluorspar concentrate assayed 98.6 percent CaF 0.50 percent SiO,, 0.34 percent CaCo 0.003 percent metallic sulfides and no complex metallic salt contaminants and represented a recovery of 83.3 percent of the fluorspar in the ore.

Example 3 exemplifies the process of the present invention.

i with the following procedure.

EXAMPLES A crude fluorspar ore assaying' 87.23 percent CaF}, 4.68 1

The ore wassubjected .to staged crushing and screening.

The crushed product was then wet ground ina ball millwith v the addition of ferrous sulfate in an amount equivalent to.

0.275 pounds per ton to produce an aqueous pulplcontaining solidshaving .aparticle size such that 89 percent passed through a 200 mesh screen. The pulp discharging from the ball mill wherein the ore was wet ground had a solids content of 70 percent, based on the weight of the pulp, and the classifier overflow was maintained to produce a pulphaving a solids content of 49 percent, based on the weight of thepulp. The water used for wet grinding of the ore, contained the equivalent of 190 p.p.m. total hardness. Separan a'commen cial flocculating agent was added to the concentrator in an amount equivalent to 0.04 pounds per ton of ore milled to assist in settling the pulp. The. aqueous pulp was then thickenedby decantation. The thickened pulp, having a solids content of about 58 percent basedon the weight of the pulp, was then transferred to a combination boil-conditioner tank). At this point there were added amountsequivalent to' 2.2

pounds per ton of stearic fatty acid, 3.3 pounds per ton of Acin tol FA2 (see Example 1) and 0.97 pounds per ton sodium 1 carbonate. The pulp was then conditioned at its boiling temperature (207F.) by introducing steam through coils in the conditioner for a period of 20 minutes. After conditioning} sufiicient water was added to the pulp to produce a pulp having a solids content of about 30 percent by weight basedon the weight of the pulp. 'At the conditioner discharge,

quebracho in an amount equivalent to 0.18 pounds perton of crude ore and sodium silicate in an amount of 3.67 pounds per ton of crude ore were added to the diluted pulp which was fed into the first cell of abank of flotation cellsto which-air was continuously introduced, thereby resulting in formation ofa compact, heavily mineralized fluorspar froth. The underflow comprisingthe tailings was rich'in gangues The' rougherfroth was then cleaned by refloating' in a series of flotation cells where quebracho was added in. two stages in amounts equivalent to 0.37 pounds per ton in each stage to further depress the carbonate gangue minerals. The final fluorspar concentrate assayed 97.48 percent CaF 1.03 percent SiO and 1.03 percent CaCO and accounted for a recovery of9 l .0 percent of the fluorspar in the ore.

Substantially similar results may tie-obtained with employ v ment of sodium metasilicate as a conditioning agent and sodium hydroxide as a pH regulator.

EXAMPLE 4 In order to demonstrate the benefit of adding ferrous sulfate I V a 55 From these data it may, be; observed that the presence of to a flurospar orewhich did not originally contain the salt in the desired amounts two series of runs wereconducted on these fluorspar ores. The ores which were processed in this ex-.

ample following the procedure describedin Example :3 analyzed as follows:

In one of the series of runs(3.test s) no ferrous sulfatewas added. In the otherseries of runs (7 tests) approximately025 to 0.33 pounds of ferrous sulfate per ton of fluorspar ore was added to the ore during the grind circuit. The process conditions of Example 3 were employed. The results of these tests I were averaged and are presented below:

l Awrage of three (3) tests. 1 Average of seven (7) tests.

From these data it maybe observedthat'the use of ferrous sulfate resulted in an increase in grade of theffluoispar' produced and a 3.8 percent increase in recovery.

l; EXAMPLES ln order to demonstrate the effectiveness of guar as an aux v iliary gangue depressant in the practice of the present process f a series of tests were conducted following the procedureof Example 3, except in one seriesof runs guar was present in adi dition to the quebracho and sodium silicate depressants. I About 0.30 pounds of guar per ton of ore was added to the K aqueous pulp during the grind circuit of the other series of runs. Ferrous sulfate was present in both series of runs in an amou'nt of about 0.25 pounds per ton of ore. The results of these runs are presented below:

( l lAverage of three (3) tests (2) Average of seven (7) tests 30. 7 FLUORSPAR 012E ANALYSIS.

can, percent 16.00 87.55 89.06 stonpercentnn 14.23 3.24 5.94 C8001, percen 6.62 2. 52 3.33

RUNS WITHOUT GUAR ADDITION .guar in addition to the quebrachoand sodium silicate consistingly gave an acid-grade .fluorspar concentrate in high yields. j i

The results of the above-described flotation procedures may also be reproduced on other flu'orsparores containing ap preciable quantities of gangue Iminerals. Metallic sulfides, quartz and silicate minerals including feldspar, clay and aspresent invention thereby enabling: a good recovery of the fluorspar as acid-grade" concentrates.

0f amounts of gangue minerals which consist essentially of a one- 1 g stepfluorspar flotation circuit comprising mixing the crude ore with water to form an aqueous pulp, adding to the aqueous asses sociated iron oxide are readily retarded by the process of the i pulp a water-soluble ferrous salt in an amount sufficient to provide between 0.2 and 0.8 pounds of ferrous salt per ton of crude fluorspar ore milled, at least one depressant for gangue minerals selected from the group consisting of alkali metal silicates, alkali metal metasilicates and quebracho, and a collector of fluorspar, said collector selected from the group consisting of saturated fatty acids, mixtures of saturated and unsaturated fatty acids wherein the saturated fatty acid content of the mixture comprises at least about 30 percent of the total quantity of collector present, and soaps thereof, conditioning this mixture by heating said pulp to its boiling point with agitation while maintaining said pulp at a pH between about 7.0 and 10.0, subjecting said pulp to froth flotation, thereby producing a froth rich in fluorspar and recovering in excess of 80 percent based on the fluorspar content in the crude ore, of acid-grade fluorspar from said froth.

2. The process of claim 1 wherein the fluorspar ore additionally contains at least one of metallic sulfides and metallic salt contaminanats.

3. The process of claim 1 wherein the water-soluble ferrous salt is ferrous sulfate.

4. The process of claim 1 wherein the saturated fatty acid content of the collector is present in an amount of at least l.5 pounds per ton of ore milled.

5. The process of claim 4 wherein the collector is a mixture of saturated and unsaturated fatty acids containing from 12 to l8 carbon atoms and the depressant is an alkali metal silicate.

6. The process of claim 1 wherein the aqueous pulp additionally has added to it prior to conditioning by heating a minor amount of guar.

7. The process of claim 6 wherein guar is added to the aqueous pulp prior to the addition of the collector.

8. The process of claim 7 wherein the guar is in contact with the aqueous pulp for about 2 to 10 minutes prior to the addition of the collector.

9. The process of claim 1 wherein guar is added to the aqueous pulp in an amount between 0.1 and 0.7 pounds per ton of fluorspar ore. I

10. The process of claim 1 wherein the collector is a saturated fatty acid containing from 12 to 18 carbon atoms.

11. The process of claim 1 wherein the collector is a mixture of saturated and unsaturated fatty acids containing from 12 to 18 carbon atoms.

12. The process of claim 1 wherein the depressant is an alkali metal silicate.

13. The process of claim 1 wherein the depressant is a mixture of an alkali metal silicate and quebracho. 

